There has long been a need for a liquid, fabric-softening, fine detergent which imparts to fabrics during the washing process desirable softening and antistatic properties. Because of the known incompatibility of conventional fabric softeners of the type of quaternary ammonium or imidazolinium compounds with anionic surfactants, it has not been possible to use anionic surfactants in these liquid preparations. Therefore, combinations of nonionic surfactants and quaternary ammonium compounds have been used. Such combinations are described in, for example, British Pat. No. 830,864, which discloses liquid detergents containing nonionic surfactants and quaternary ammonium compounds having a long-chained alkyl radical and three short-chained alkyl radicals. According to the Journal Seifen-Oele-Fette Wachse (1963), 4, p. 78, the washing power of these combinations of nonionic surfactant and quaternary ammonium compound is particularly good if the ratio of the nonionic surfactant to the quaternary ammonium compound is in a quantitative ratio of 4:1 to 1:1.
Other nonionic surfactant-quaternary ammonium compound compositions are known. For example, DOS No. 2,426,581 describes a combination of a nonionic surfactant, a customary softening quaternary ammonium compound with one or two long-chained alkyl radicals, as well as another quaternary ammonium compound with one methyl group, one or two long-chained alkyl groups, and one or two polyglycol ether groups. A liquid detergent comprised of a nonionic surfactant of the type of alkyl polyglycol ethers or alkylphenol polyglycol ethers, and a conventional fabric softener of the type of difat-alkyl-dimethyl-ammonium halides, as well as of a fatty acid polyglycol diester, is known from DOS No. 2,529,444.
These liquid detergent compositions have not, however, been satisfactory, because no balance between washing power, fabric softening capacity, and sudsing behavior, could be achieved. Moreover, there has been no suggestion in the art as to the optimum composition of a liquid detergent to obtain an optimum combination of the desired properties. Rather, the man skilled in the art has had to assume that a wash-active surfactant would detach the fabric softener contained in the wash liquor together with the soil from the textile fibers and remove it altogether so that the desired fabric-softening effect would not be achieved; conversely, good softening effect would be achieved only with a surfactant having insufficient cleaning ability.